Thermostat



April 1942- M. J. SCHOUMAKER 2,279,929

THERMOSTAT Filed March 11, 1940 Aiiorne gs Patented Apr. 14 1942THERMOSTAT Mitchell J. Schonmaker, Minneapolis, Minn, as-

signor of one-fourth to Joseph G. Haeg Application March 11, 1940,Serial No. 323,256

8Ciaims.

My invention relates to temperature responsive electric circuitcontrolling apparatus and particularly to a contact making thermostat.Various types of thermostats for use in connection with fire alarmsystems and other control systems are available, but are mostly ofconstruction which is relatively expensive.

An object of my invention is to provide a particularly compact andsimple form of electrical contact making thermostat wherein duplicatepairs of contacts are connected in multiple.

Another object of my invention is to provide such a thermostatcomprising a minimum of parts and including, other than fasteningscrews, only a single type of metallic part.

Still another object is to provide such a thermostat wherein a pair ofidentical bimetallic parts are so constructed that one portion of onesuch part cooperates with another portion of a duplicate part to.comprise a pair of electrical contacts and also wherein a pair of suchparts provide for two pairs of electrical contacts.

A further object is to provide such a thermostat of light, compact,simple, rugged and inexpensive construction.

These and other objects and advantages of the invention will more fullyappear from the following description made in connection with theaccompanying drawing, wherein like reference characters refer to thesame parts throughout the views, and, in which:

Fig. 1 is a top view of an embodiment of my invention with the coverthereof removed;

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1, asindicated by the arrows; and

Fig. 3 is a sectional View taken along the line 3-3 of Fig. 1, asindicated by the arrows.

Referring to the drawing I provide for the purpose of supporting andhousing other parts of the particular embodiment of the invention whichis illustrated, a relatively long and narrow open topped rectangular box4 having at its lower side an outwardly projecting rectangular flange 4ain which are apertures 4b to accommodate means for attaching the flange4a to a flat surface. The box' 4 includes end walls 4c and side walls4d. and if desired the entire box inclusive of the flange 4a may bemolded in one piece from plastic material. The primary requirement inregard to the material from which the box 4 is made is that thismaterial be an electrical insulator.

Within the box 4 I provide a thermostat structure consisting of twobimetallic plates 5 which are placed against the inner sides of thelongitudinal side walls 4d of the box 4. At the ends of the plates 5blocks lie of insulating material may be placed between thecorresponding end portions of the respective plates 5, as indicated inFigs. 1 and 2. The blocks 4e may be formed integrally with the box 4.

Each of the plates 5 is provided with a longitudinal slot 5a extendingfrom one end of the plate 5 to a point short of the remaining end so asto divide the plate 5 into a mounting base portion 5b and a swingablearm portion which is connected by the unslotted end portion 5e of theplate 5. The two plates 5 are so arranged in the box 4 that theunslotted ends 5e of the respective plates 5 are at opposite ends of thebox 4.

Each of the plates 5, in the attachment base portion 5b thereof, isapertured and internally screw threaded at points near the respectiveends thereof and, in registration with these screw threaded portions ofthe plate 5, the longitudinal side walls 4d of the box 4 are providedwith external bosses 4f and are apertured. Screws 5 of a headed type areinserted through the bossed and apertured portions of the box 4 and arescrewed into the internally screw threaded portions of the plates 5 tosecure the plates 5 to the longitudinal side walls 4d of the box 4. Thescrews 5 also constitute electrical terminal screws for the respectiveplates 5.

The bimetallic plates 5 are faced in such directions that the swingablearm portions 50 thereof will swing away from the corresponding box wall4d responsive to change in temperature in a selected direction. Forexample, if the thermostat is to be used in connection with a fire alarmsystem the plates 5 are so faced that the swingable arms thereof willflex outwardly from the corresponding box walls 4d responsive to anincrease in temperature.

The free ends of the swingable arm portions 5c are formed intoelectrical contact elements and in the embodiment illustrated this isdone by bending the free end portion 5d of the swingable arrn 5c of eachplate 5 toward the other plate 5, as indicated in Figs. 1 and 3.Preferably the free end portions 5d are tapered so that the ends thereofare relatively narrow. When the arms 50 flex responsive to temperaturechange each of the free ends 5d of the arms 50 will engage the unslottedportion 5e of the other plate 5,,whereby the respective plates 5 willbecome electrically interconnected. It should be apparent that the twocontact elements 511 in cooperation with the two unslotted end portions5e of the respective plates 5 comprise two pairs of electrical contactswhich are connected in multiple and which will make contact responsiveto the same variation in temperature. Should any foreign materialinterfere with engagement of one of these pairs of contacts a factor ofsafety is provided in that the other pair of contacts is available forclosing the circuit.

A rectangular centrally apertured cover plate 1 is provided, themarginal portion of which is shouldered, as indicated in Fig. 2, to fitthe upper edges of the end and side walls 40 and 4d of the box 4. Thecenter of the upper side of the bottom wall 49 of the box 4 is providedwith an upstanding recessed and internally screw threaded boss 4h intowhich a cover securing screw 8 projecting downwardly through the centralaperture through the cover I may be screwed.

From the above described it will be seen that the slotted and aperturedplates 5 are identical in construction and hence that only one type ofmetallic part other than the screws 6 and 8 is involved in theconstruction of my thermostat. It will further be seen that the screws 6perform dual functions, that is they serve both to secure the plates 5to the walls of the box 4 and as electrical terminals for the plates 5.In using the screws 6 as electrical terminals the screws may be loosenedfor insertion of the looped or hook shaped ends of wires under the headsthereof whereafter each loosened screw 6 may be again tightened tosecure the wire and resume its function of securing the plate 5 to thebox wall. In a two wire circuit connected to a plurality of thermostatunits wires extending to the thermostat unit from one direction may beattached thereto by means of the screws 6 at one end of the thermostatunit, and wires extending from the thermostat unit in the otherdirection may be connected to the thermostat unit by means of the screws6 at the remaining end of the thermostat unit so that the wire circuitwill be connected to the thermostat unit and will be continued throughthe base portions of the plates 5 of the thermostat unit.

It is apparent that I have invented a novel and particularly simple,light, compact, reliable and inexpensive type of contact makingthermostat unit.

It will, of course, be understood that various changes may be made inthe form, details, arrangement and proportions of the various partswithout departing from the scope of my invention.

What is claimed is:

1. A thermostat comprising, a pair of relatively long, generallyrectangular bi-metallic plates, each of said plates being longitudinallyslotted from one end thereof to a point short of the remaining endthereof to divide the plate into a mounting base and a swingable arminterconnected by the unslotted end portion of the plate, a supportingstructure to which the base portions of said plates are secured inmutually facing, parallel, spaced relation with the unslotted portionsof said plates at opposite ends, said plates being so faced that the armof each will flex toward the unslotted portion of the other responsiveto a temperature change in a predetermined direction, the free end ofthe arm of each plate being formed into an electrical contact elementfor engagement with the unslotted end portion of the other plate, andelectrical terminals connected to said respective plates.

2. A thermostat comprising, a pair of relatively long, generallyrectangular bi-metallic plates, each of said plates being longitudinallyslotted from one end thereof to a point short of the remaining endthereof to divide the plate into a mounting base and a swingable armjoined by the unslotted end portion of the plate, a supporting structurecarrying said bases in spaced, parellel, mutually facing relation withthe unslotted portions of said plates at opposite ends, said platesbeing so faced that the arm of each will flex toward the unslottedportion of the other responsive to a temperature change in apredetermined direction, the free end of the arm of each plate beingbent toward the other plate and formed into an electrical contact forengagement with the unslotted portion of the other plate, and electricalterminals connected to said respective plates.

3. A thermostat unit comprising, a relatively long and narrow, opentopped box having parallel, spaced side walls, a pair of rectangularbimetallic plates secured in their lower portions to the inner sides ofsaid respective side walls, said plates being longitudinally slottedfrom respectively opposite ends thereof to points short of the remainingends thereof to divide each plate into a base portion and a swingablearm connected by the unslotted end of the plate, each of said platesbeing so faced that the arm portion thereof will flex toward theremaining plate responsive to a temperature change in a predetermineddirection, and the free end of each of said arms being formed into anelectrical contact element engageable with the unslotted end of theother plate responsive to flexure of the arm, and electrical terminalsconnected to the respective plates.

4. A thermostat unit comprising, a relatively long and narrowopen-topped box having parallel, spaced side walls, a pair ofrectangular bimetallic plates placed in said box against the inner sidesof said respective side walls, said plates being longitudinally slottedfrom respectively opposite ends thereof to points short of therespective remaining ends thereof to divide each plate into anattachment base and a swingable arm joined together by the unslotted endportion of the plate, each of said plates being so faced that the armportion thereof will flex toward the remaining plate responsive to atemperature change in a predetermined direction, the free end of the armof each of said plates being formed into an electrical contact elementengageable with the unslotted end portion of the other plate responsiveto flexure of the arm, said side walls and said bases being apertured inregistering portions thereof, and elements extending through saidrespective registering pairs of apertures to secure said bases to saidside walls and to function as electrical terminals for said respectiveplates.

5. A thermostat unit comprising, a relatively long and narrowopen-topped box having parallel, spaced side walls, a pair ofrectangular bimetallic plates placed in said box against the inner sidesof said respective side walls, said plates being longitudinally slottedfrom respectively opposite ends thereof to points short of therespective remaining ends thereof to divide each plate into anattachment base and a swingable arm joined together by the unslotted endportion of the plate, each of said plates being so faced that the armportion thereof will flex toward the remaining plate responsive to atemperature change in a predetermined direction, the free end of the armof each of said plates being formed into an electrical contact elementengageable with the unslotted end portion of the other plate responsiveto flexure of the arm, each of said bases being apertured and internallyscrew-threaded in longitudinally spaced portions thereof and respectiveregistering portions of said side walls being apertured, and headedscrews projecting through the apertured portions of said side walls andscrewed into the screw-threaded portions of said bases to secure saidbases to said side walls and to constitute electrical terminals for saidrespective plates accessible from the outside of said box.

6. A thermostat comprising, a relatively long bimetallic plate, saidplate being longitudinally slotted from one end thereof to a point shortof the remaining end thereof to divide the plate into a mounting baseand a swingable arm interconnected by the unslotted end portion of theplate, a supporting structure upon which said plate is mounted, anelectrical terminal secured to each end of said mounting base, a secondplate of electrically conductive material mounted upon said supportingstructure and comprising a contact element engageable by said swingablearm on said first plate upon flexing of said arm under temperaturechanges, and said second plate being substantially co-extensive withsaid first plate and having an electrical terminal connected to each endthereof.

7. A thermostat comprising, a pair of relatively long bi-metallicplates, each of said plates being longitudinally slotted from one endthereof to a point short of the remaining end thereof to divide saidplate into a mounting base and a swingable arm interconnected by theunslotted end portion of the plate, a supporting structure upon whichsaid plates are mounted in spaced relationship, said plates being sopositioned that the arm of each will flex toward and engage a portion ofthe other plate responsive to a temperature change, the free end of thearm of each plate constituting an electrical contact element forengagement with the other plate and electrical terminals connected tosaid respective plates.

8. A thermostat comprising, a relatively long electrically conductivebi-metallic plate slotted from one end thereof to a point short of theother end thereof to divide the plate into an electrically conductivemounting base and a swingable contact arm joined together by theunslotted portion of said plate, a non-conducting supporting structurefor said plate, an electrical terminal at each end of said mounting baseportion of said plate, and an electrical contact element mounted on saidstructure in position for engagement by said contact arm as a result offlexing of said arm responsive to a temperature change.

MITCHELL J. SCHOUMAKER.

